I have the Clifford 600 on mine. Excellent bit of kit as long as it is installed by a good fitter.
The standard cat 1 alarm/immobilisors from most manufacturers are about £300-£400. The Clifford 600, in my opinion is worth the extra because of the extra features and is impossible to bypass, - I think.
Saying that I live in a fairly high risk area so I was prepared to spend the extra. You may not have the same problem in the Highlands.
I bet you have some great driving roads.
Neil.